Recently, studies and developments of semiconductor lasers (LD) have been being promoted actively for applications, such as pickups for optical disks, processing and pointers, and further television sets and projectors. Among such applications, the particular applications require high-power driving of LDs. In these applications, heat generation from the LDs is large, and therefore improvement in heat dissipation is strongly demanded.
For a high-power LD, a method called junction-down mounting is typically used in order to improve the heat dissipation. In this method, the vicinity of an active layer, which is the main heating portion in the LD, is mounted near a heat dissipation member to improve the heat dissipation.
In what is known as a ridge-waveguide semiconductor laser, which has a ridge-shaped stripe, the side surface of a ridge is buried with a metallic oxide-based insulating film of ZrO2, SiO2 or the like having a very poor thermal conductivity. Therefore, when junction-down mounting is performed, less heat can conduct from an active layer portion directly under the ridge, which functions as the main heat source, via an insulator area of the side surface of the ridge. This becomes a factor in reducing the heat dissipation.
For example, a technique of burying the side surface of the ridge with AlN or AlGaN having a high thermal conductivity rather than the metallic oxide-based insulating film is proposed. For example, a technique of burying the side surface with AlON having a high thermal conductivity is also proposed.
Nitride-based materials, such as AlN, AlGaN and AlON, however, have large membrane stresses compared to metallic oxide-based materials. Accordingly, it is feared that minute cracks might be made in a semiconductor layer to cause adverse influence on reliability of elements.